Acids and Bases: Define Acids and Bases: Define pH/pOHpH/pOH

At the conclusion of our time At the conclusion of our time together, you should be able to:together, you should be able to:

1. Define pH and pOH2. Explain the pH scale and what it means3. List 3 different ways to test for pH

Law of ProbabilityLaw of Probability

-The probability of  being watched is -The probability of  being watched is directly proportional to the stupidity of your directly proportional to the stupidity of your  act act

What is pH???What is pH???

p = countp = count H = Hydronium ionH = Hydronium ion (H(H33OO++)) In 1 Liter of water, (55+ moles of water), In 1 Liter of water, (55+ moles of water),

how many moles of hydronium ions are how many moles of hydronium ions are there???there???

Understanding pH gives me this Understanding pH gives me this number!!!number!!!

If there was 1 mole of HIf there was 1 mole of H33OO++ in 1 Liter of in 1 Liter of

water, (55+ moles of water), this count water, (55+ moles of water), this count would be 1 mole.would be 1 mole.

Remember: pH = - log [H+]Remember: pH = - log [H+]

pH = -log[1]pH = -log[1] Therefore, by definition, the pH of this Therefore, by definition, the pH of this

solution is solution is = 0= 0

HH22O + HO + H22O O ---> ---> HH33OO++ + OH + OH--

<===<=== This equation indicates that most water This equation indicates that most water

molecules stay as molecules, very few will form molecules stay as molecules, very few will form hydronium ionshydronium ions

If we count the number of hydrogen ions in one If we count the number of hydrogen ions in one liter of water (pH) we would get:liter of water (pH) we would get:

.0000001 moles of H.0000001 moles of H33OO++/liter of water/liter of water

or 10or 10-7-7 moles of H moles of H33OO++/liter of water/liter of water

What is the pH of water??What is the pH of water?? pH = 7pH = 7

HH22O + HO + H22O O ---> ---> HH33OO++ + OH + OH--

<===<=== This equation indicates that most water This equation indicates that most water

molecules stay as molecules, very few will form molecules stay as molecules, very few will form hydroxide ionshydroxide ions

If we count the number of hydroxide ions in If we count the number of hydroxide ions in one liter of water (pOH) we would get:one liter of water (pOH) we would get:

.0000001 moles of OH.0000001 moles of OH--/liter of water/liter of water or 10or 10-7-7 moles of OH moles of OH--/liter of water/liter of water What is the pOH of water??What is the pOH of water?? pOH = 7pOH = 7

Since 1 mole of OH- in one Liter of water Since 1 mole of OH- in one Liter of water would be a pOH = 0would be a pOH = 0

And the pH and pOH of water is 7 or neutral,And the pH and pOH of water is 7 or neutral, Therefore, the pH of a strong base with a Therefore, the pH of a strong base with a

pOH of 0 would be?pOH of 0 would be? pH = 14pH = 14 Therefore, the pH scale goes from 0-14Therefore, the pH scale goes from 0-14 Also, any pH can be converted to pOH by?Also, any pH can be converted to pOH by? Subtracting from 14.Subtracting from 14.

pH- The Amount Of H+ Ions In A Solution.

ACID extra H+1 ions (protons)

BASE fewer H+1 ions.

extra OH-1 ions.

1 2 3 4 5 6 7 8 9 10 11 12 13 14

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Right Where You Left Him.Right Where You Left Him.

Maybe Our Goals Aren’t the Exact Same, But They’re Similar!!

There are several ways to test pHThere are several ways to test pH Blue litmus paper (red = acid)Blue litmus paper (red = acid) Red litmus paper (blue = basic)Red litmus paper (blue = basic) pH paper (multi-colored)pH paper (multi-colored) pH meter (7 is neutral, <7 acid, >7 pH meter (7 is neutral, <7 acid, >7

base)base) Universal indicator (multi-colored)Universal indicator (multi-colored) Indicators like phenolphthaleinIndicators like phenolphthalein Natural indicators like red cabbage, Natural indicators like red cabbage,

radishesradishes

Paper tests like litmus paper and pH Paper tests like litmus paper and pH paperpaper Put a stirring rod into the solution Put a stirring rod into the solution

and stir.and stir. Take the stirring rod out, and Take the stirring rod out, and

place a drop of the solution from place a drop of the solution from the end of the stirring rod onto a the end of the stirring rod onto a piece of the paperpiece of the paper

Read and record the color Read and record the color change. Note what the color change. Note what the color indicates.indicates.

Use a small portion of the paper. Use a small portion of the paper. You can use one piece of paper You can use one piece of paper for several tests.for several tests.

pH Paper

Blue Litmus paper

Red Litmus paper

Indicators are dyes that can Indicators are dyes that can be added that will change be added that will change color in the presence of an color in the presence of an acid or base.acid or base.

Some indicators only work Some indicators only work in a specific range of pHin a specific range of pH

Once the drops are added, Once the drops are added, the sample is ruinedthe sample is ruined

Some dyes are natural, like Some dyes are natural, like radish skin or red cabbageradish skin or red cabbage

Tests the voltage of the Tests the voltage of the electrolyteelectrolyte

Converts the voltage to pHConverts the voltage to pH Expensive, accurateExpensive, accurate Must be calibrated with a Must be calibrated with a

buffer solutionbuffer solution

We’ll Chip Away at this a Little at a Time!!

Acids and Bases: pH/pOHAcids and Bases: pH/pOHLet’s see if you can:Let’s see if you can:

1. Define pH and pOH2. Explain the pH scale and what it means3. List 3 different ways to test for pH

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Choking Sign has been revised:Choking Sign has been revised:

Old Sign:Old Sign:

New Sign:New Sign:

Get Your Clicker!!!

The “p” in pH stands for?The “p” in pH stands for?

1.1. PriorityPriority

2.2. CountCount

3.3. NumberNumber

4.4. MolarityMolarity

5.5. Not listedNot listed

The “H” in pH stands for?The “H” in pH stands for?

1.1. HouseHouse

2.2. Hydrogen ionsHydrogen ions

3.3. AcidAcid

4.4. ConcentrationConcentration

5.5. Not listedNot listed

Red litmus paper will turn what color in Red litmus paper will turn what color in an acid?an acid?

1.1. BlueBlue

2.2. WhiteWhite

3.3. RedRed

4.4. ClearClear

5.5. Not listedNot listed

Which of the following would be the most Which of the following would be the most accurate way to test for pH?accurate way to test for pH?

1.1. pH meterpH meter

2.2. Litmus paperLitmus paper

3.3. Phenylthalein Phenylthalein

4.4. Cabbage juiceCabbage juice

5.5. Universal indicatorUniversal indicator

6.6. Not listedNot listed

Several liquids are tested for pH. Which Several liquids are tested for pH. Which of these liquids would be the weakest of these liquids would be the weakest

acid?acid?

1.1. Liquid a, pH = 1.0Liquid a, pH = 1.0

2.2. Liquid b, pH = 4.5Liquid b, pH = 4.5

3.3. Liquid c, pH = 6.5Liquid c, pH = 6.5

4.4. Liquid d, pH = 8.5Liquid d, pH = 8.5

5.5. Liquid e, pH = 10.5Liquid e, pH = 10.5

6.6. Liquid f, pH = 13.0Liquid f, pH = 13.0